Dogtooth tunaDOT
Gymnosarda unicolor

Characteristic features:

  • Well developed median keel with 2 smaller keels on either side of caudal peduncle
  • Lateral line strongly undulating
  • Teeth large and conical
  • Tongue with 2 patches of teeth
  • 11–14 gill rakers on first gill arch
  • 6–7 dorsal finlets, 6 anal finlets
  • Interpelvic process single, large

Colour:

Bright bluish black above and silvery below, no stripes or spots on sides. Second dorsal fin blackish with white tip, anal fin black-grey with white tip, other fins greyish.

Size:

Up to 220 cm TL, and up to 131 kg in weight.1

Distribution:

Found in tropical waters of the Indo-West Pacific.

Habitat:

Pelagic, associated with reef drop-offs. Found at depths from the surface to 300 m.

Biology:

Gymnosarda unicolor feeds primarily on small fish and squid. They are highly migratory, generally solitary or forming small schools of 6 or less. Maturity varies on location, off the coast of India, length at first maturity is estimated at 65–70 cm FL for both females and males.2,3 Gymnosarda unicolor spawn year round, with a peak during August–January. Estimated maximum age is 12 years.3

Indonesian fisheries:

No direct fishery exists but is regularly caught by pole-and-line, also hand lines and trolling.

Similar species:

Grammatorcynus bilineatus
Double-lined mackerel
Grammatorcynus bilineatus
Grammatorcynus bilineatus differs in having 2 lateral lines (vs. single and strongly undulating); a single rectangular patch of teeth on tongue (vs. 2 patches of teeth on tongue); interpelvic process small and single (vs. large and single) and a body covered in moderately small scales (vs. scaleless behind a scaled corselet).

 

Scomberomorus spp.
Seer fishes
Scomberomorus commerson
Scomberomorus spp. differ in having a strongly compressed body (vs. moderately compressed); upper jaw reaching almost to posterior margin of eye, or slightly beyond (vs. upper jaw reaching to middle of eye); anal-fin origin below midpoint or origin of second dorsal fin (vs. anal-fin origin level with of second dorsal fin); 2 patches on teeth on upper surface of tongue (vs. no patches of teeth) and markings in the form of dark vertical bars or spots (vs. no markings on body).

 

Thunnus spp.
True tuna
Thunnus albacares
Thunnus albacares
Thunnus spp. differ in having the anterior portion of the first dorsal-fin greater in height than posterior (vs. of same height); interpelvic process 2 flaps (vs. single); first dorsal fin without dark markings (vs. anterior tip dark) and markings in the form of  silver, complete or broken vertical bars or spots, or a series of alternating vertical bars and rows of spots (vs. no markings on body). Note – markings on Thunnus may fade when condition is lost.

References

1.
Collette BB, Nauen CE. FAO species catalogue. Volume 2. Scombrids of the world. An annotated and illustrated catalogue of tunas, mackerels, bonitos and related species known to date. 1983.
2.
Sivadas M, Anasu Koya A. On the fishery and some aspects of the biology of dogtooth tuna, Gymnosarda unicolor (Ruppell) from Minicoy, Lakshadweep. Journal of the Marine Biological Association of India. 2005;47(1):111–3.
3.
Joshi KK, Abdussamad EM, Koya KP, Sivadas M, Kuriakose S, Prakasan D, et al. Fishery, biology and dynamics of dogtooth tuna, Gymnosarda unicolor (Rüppell, 1838) exploited from Indian seas. Indian Journal of Fisheries. 2012;59(2):75–9.